SWI/SNF complexes shape 3D chromatin architecture through CTCF and cohesin.

ARID1A loss and pharmacological BAF inhibition increase accessibility at CTCF-binding sites and strengthen CTCF/SMC3 occupancy, reshaping 3D genome organization in mammalian cells.

• Why it matters: BAF component LOF mutations are frequent across cancer types, but a conserved mechanism linking SWI/SNF disruption to chromatin architecture changes has been unclear.
• What they did: The authors inhibited BAF pharmacologically and deleted ARID1A across mammalian cell types and tissues, then used genomic profiling to measure CTCF and SMC3 occupancy and 3D genome contacts.
• The result: cBAF loss strengthened topologically associating domain boundaries, replaced long-range enhancer-promoter loops with shorter promoter-proximal loops at CTCF-enriched sites, and in vivo Arid1a deletion expanded a proliferative population whose phenotype was fully reversed by Ctcf or Pbrm1 deletion.